1. Field of the Invention
The present invention relates to a motor power interrupting device of an injection molding machine, which interrupts power of a servo motor.
2. Description of the Related Art
An injection molding machine manufacturer lines up various sizes of machines which are different in specifications such as a mold clamping force, an injection pressure, and an injection capacity, so as to form molded articles having various sizes by the injection molding machine. The injection molding machine is provided with a mold opening and closing mechanism, a molded article ejection mechanism, an injection mechanism and a screw rotation mechanism, and a servo motor is used for driving each of the mechanisms.
One servo motor is generally used in each of the mechanisms of the injection molding machine, however, in the case where it is desired to generate great mold clamping force or great injection pressure, great output is generated by synchronously actuating a plurality of servo motors, or the great output is generated by employing a plural winding type servo motor which is provided with a plurality of coils of the servo motor in spite of one serve motor (refer to Japanese Patent Application Laid-Open No. 2003-189657).
The same number of servo amplifiers as the number of the coils of the servo motor are necessary, in which the servo amplifiers drive the servo motors. Accordingly, in the case where a plurality of servo motors are used or the plural winding type servo motor is used, the number of the servo amplifiers used in one injection molding machine is necessarily increased even if the number of the actuating mechanisms is not changed. Some of servo amplifiers have a plurality of servo motor driving means in one servo amplifier unit. The servo motor driving means indicates means which supplies to the coils of the servo motor the electric power for driving the servo motor. Therefore, in the present invention, the servo amplifier in which a plurality of servo motor driving means are provided in one unit is assumed as an assembly of a plurality of servo amplifiers.
The injection molding machine is classified broadly into a mold clamping mechanism portion and an injection mechanism portion. In order to facilitate work for taking the molded articles out of the mold and work for removing resin discharged from an injection nozzle, a movable door is provided in each of a mold area and an injection nozzle area. The mold area is at risk of having a worker be pinched by the molds. The injection nozzle area is at risk of having the worker be burned by the resin discharged out of the nozzle. The injection molding machine is provided with a safety function which protects the worker doing maintenance of the injection molding machine from the risks, and secures safety of the worker.
As the safety function, the movable door is provided with a switch, and is structured such that a signal for interrupting the power of the servo amplifier is output from the switch according to the opening of the movable door (refer to Japanese Patent Applications Laid-Open Nos. 60-262617, 62-208920 and 2002-361703). For example, a servo motor for opening and closing the mold and a servo motor for ejecting molded articles are attached to the mold clamping mechanism portion, and in the case where the movable type door in the mold area opens, the power of the servo motor of the mold clamping mechanism portion is interrupted by detecting a state signal of the movable type door. A servo motor for injecting and a servo motor for rotating a screw are attached to the injection mechanism portion, and in the case where the movable type door in the injection nozzle area opens, the power of the servo motor of the injection mechanism portion is interrupted by detecting a state signal of the movable type door in the injection nozzle area.
The number of the servo amplifiers mounted to the injection molding machine is different according to the specification of the machine, as mentioned above. Further, at least one power interrupting means for interrupting the power of the servo motor is necessary in relation to one servo amplifier.
FIG. 6 is a view describing a mechanism for interrupting power of a conventional servo motor.
In an injection molding machine shown in FIG. 6, the powers of the respective servo motors 13, 16, 26 and 29 provided in the injection molding machine are interrupted by interruption request signals which are output from a controller 90 to respective servo amplifiers 45 46, 47, 41, and 43 driving the servo motors, and interruption confirmation signals for confirming the interruption of the power are output to the controller 90, in the respective servo amplifiers 45, 46, 47, 41 and 43. In FIG. 6, reference numerals 80, 82, 84, 86 and 88 denote interruption request signal transmitting means, reference numerals 81, 83, 85, 87 and 89 denote interruption confirmation signal receiving means, and reference numerals 14, 17, 27 and 30 denote position/speed detectors connected to the respective servo motors 13, 16, 26 and 29.
A problem of the injection molding machine exists in a point that in the case where the number of the servo amplifiers varies according to the machine specification, the corresponding number of interruption request signals to the controller are necessary according to the increase of the number of the servo amplifiers, and a cost increase is caused, in the structure shown in FIG. 6.